Classic nonketotic hyperglycinemia and symmetrical intrauterine growth retardation, diagnostic challenges, and fatal outcome: a case report and review of the literature

Nonketotic hyperglycinemia typically presents with lethargy, hypotonia, seizures, and apnea, often fatal in the neonatal period. Glycine's dual role as an excitatory and inhibitory neurotransmitter explains the seizures and hypotonia seen in nonketotic hyperglycinemia. While acute symptoms may resolve, survivors face severe neurological impairment. Early recognition of nonketotic hyperglycinemia is critical for genetic counseling and palliative care. This case highlights the diagnostic challenge of nonketotic hyperglycinemia, particularly when presenting with intrauterine growth restriction, which can mimic other neonatal conditions such as sepsis or hypoxic-ischemic encephalopathy. Consanguinity and prior fetal loss should raise suspicion for metabolic disorders, and according to this case presentation, symmetric intrauterine growth restriction in high-risk pregnancies should prompt metabolic screening. Despite advances, nonketotic hyperglycinemia remains a devastating condition with high mortality and neurodevelopmental morbidity, emphasizing the importance of further research and early intervention strategies.